The Cossack Hetmanate, officially the Zaporozhian Host or Army of Zaporozhia, is a historical term for the 17th–18th centuries Ukrainian Cossack state located in central Ukraine. It existed between 1649 and 1764, although its administrative-judicial system persisted until 1782.

The Pereiaslav Agreement or Pereyaslav Agreement was an official meeting that convened for a ceremonial pledge of allegiance by Cossacks to the Tsar of Russia in the town of Pereiaslav, in central Ukraine, in January 1654. The ceremony took place concurrently with ongoing negotiations that started on the initiative of Hetman Bohdan Khmelnytsky to address the issue of the Cossack Hetmanate with the ongoing Khmelnytsky Uprising against the Polish–Lithuanian Commonwealth and which concluded the Treaty of Pereiaslav. The treaty itself was finalized in Moscow in April 1654.